object DistanceFinder {
/** Finds the maximum distance (absolute index difference) between two numbers in an array.
*
* @param arr
* The input array of integers.
* @param num1
* The first target number.
* @param num2
* The second target number.
* @return
* Some(distance) if both numbers exist, or None if either is missing.
*/
def maxDistanceBetweenNumbers(arr: Array[Int], num1: Int, num2: Int): Option[Int] = {
// Variables to track the first and last occurrences of both numbers
var first1: Int = -1
var last1: Int = -1
var first2: Int = -1
var last2: Int = -1
// Single pass through the array: O(N) time complexity, O(1) space complexity
for ((current, i) <- arr.zipWithIndex) {
if (current == num1) {
if (first1 == -1) first1 = i // Record the first time num1 appears
last1 = i // Continuously update the last time num1 appears
} else if (current == num2) {
if (first2 == -1) first2 = i // Record the first time num2 appears
last2 = i // Continuously update the last time num2 appears
}
}
// Edge case: If either number is not present in the array, return None
if (first1 == -1 || first2 == -1) {
None
} else {
// The maximum distance is always between the outermost boundaries of the two sets:
// 1. Distance between the first occurrence of num1 and the last occurrence of num2
// 2. Distance between the last occurrence of num1 and the first occurrence of num2
val dist1 = math.abs(first1 - last2)
val dist2 = math.abs(last1 - first2)
Some(math.max(dist1, dist2))
}
}
def main(args: Array[String]): Unit = {
// --- Example Usage ---
val array = Array(2, 3, 7, 3, 3, 4, 8, 8, 8, 11, 9, 1, 3)
val number1 = 3
val number2 = 8
maxDistanceBetweenNumbers(array, number1, number2) match {
case Some(distance) =>
println(s"The maximum distance between $number1 and $number2 is: $distance")
case None =>
println(s"One or both numbers ($number1, $number2) were not found in the array.")
}
}
}
/*
run:
The maximum distance between 3 and 8 is: 7
*/
